I have 'inherited' an XL1s at my current job and have been experienceing the focus problems that many others have complained about.

A lot of the articles talk about taking 'critical focus' as the solution to the problem, but that is exactly where the problem lies. Zoomed all the way in, on Manual Focus, I take focus, then zoom back out. Technically I should be able to zoom around at will within that depth of field and everything should be sharp. As others can attest, the focus does not stay sharp, even on Manual Focus and on Manual camera setting (i.e. not green setting).

I am not comforted when reading about "Canon's New Way to Focus" (Scott Barber's article from this site). A lens should act like a lens.

I have tried the 16x Manual Lens and am very pleased with the results. I will be buying one, but find it absurd that I have to spend an extra $1400 to make the camera I received from Canon usable, at least on a professional level. I'm guessing that Canon assumes (probably correctly) that the average (read: consumer) user will not notice the problem.

Welcome Jonathan,
One of the most common mistakes people make with this lens, and a source of endless problem reports like yours, is to pull manual focus by zooming all the way into the subject as close as possible. The 16x IS II lens is not a constant aperture lens. That is, its maximum aperture at its maximum telephoto position is f/2.6. At its widest position it's f/1.6.

Depending on your lighting conditions this can cause some apparent softness as you pull back from close focus. Typically, the problem cycle goes like this. Zoom to maximum telephoto, set focus, probably not noticing that the effective iris may have closed-down to f/2.6. Pulling back to re-frame the shot you notice that you're underexposed so you open the iris. Bang. You just made your shot soft due to the relationship between iris and depth of focus.

The solution is to ensure that you zoom-in only close enough to get your focus, but not so far out that the effective aperture changes.

I suspect that the lens' effective aperture shift is the real culprit behind much of the "bad focus" rap this lens as received.

Thanks for the reply, Ken.

Will the camera automatically reset to f1.6 if I zoom out from full telephoto, since that is the largest aperature it allows when wide, or, as in your example, do I have to be the one opening up b/c I detect a dark image?

I'll run a test, as your example does make sense.

And yet, I definitely recall situations where I have not changed the iris after taking critical focus and still had problems (thus my question above).

FYI: I have sent the lens in to Canon to have it reset to spec, and it has come back with the same focus problem.

when you notice the problem, what aperture are you shooting at?

<<<-- Originally posted by Jonathan Lutz : Thanks for the reply, Ken.

Will the camera automatically reset to f1.6 if I zoom out from full telephoto, -->>>

No, it will remain at f/2.6. That's the essence of the matter.

It's also worth noting that all photographic lenses generally have a sweet spot of best focus and least distortion. My casual observation, and those of others, suggests that for these lenses it's around f/5.6. On both the manual and auto lenses that -seems- to be where the best edge-to-edge sharpness occurs.

I'm certainly not asserting that your lens could not be defective. It might be. But I'd bet it isn't.

Another test to perform:

Zoom in all the way. Focus.

Slowly zoom out all the way.

Now slowly zoom back in all the way.

Still in focus throuout the zoom range? No? Then you're experiencing the same chronic problem I had which was solved only by getting the 16x manual lens. Sending it back to Canon didn't help at all.

Every once in a whiile someone sells a used one here.

Dean Sensui
Base Two Productions.

I dunno, I had the backfocus problem.I did some tests , enogh light to have about F5.6 zoomin tight set focus then zoom out the image would shift out of focus.Everything on manual including whitebalance and gain on " 0" zoom back in tight and it would now be in focus.Always being careful not to touch the focus ring even slightly.Sent it to Canon ( Toronto,Canada)specifically stating the backfocus error and since backfocus is only adjustable electronically the techs there adjusted it.It came back about 95% righton.Your problem sounds like a back focus issue.Maybe I was lucky
smitty

The Automatic lenses can not perform focus and zoom actions from the operator at the same time. It will do the focusing automatically (for the most part) while zooming. It took me forever to realize this with my camera when I would try to approach a subject at full zoom, zooming out while getting closer (y'know, for that 'seperating' look). I tried my best to keep the subject in focus while zooming, and I would still have a problem doing so. Come to find out, the lens does not let you focus while zooming. This is one reason I want to get the 16x manual lens, to have better control over what I shoot and how. Overall though, I am very happy with the IS II.

is the 16x II the one sold with the Xls1? and the manual16x some other beast? i dont understand these threads talking about trying to find a manual focus 16x cause of the hunting/zooming/focus problems? curious, i have not seen it with mine yet, but i do mostly studio work on manual anyway. thanks!
jigs

http://www.dvinfo.net/canon/articles/article82.php

This article helped me to decide on the 16x Manual Zoom.

Jiggy: Yes the 16x II lens is the one that comes with the XL1S.
If you want a complete manual lens, you have to buy them seperately (they are rather expensive, but hey, lenses always are). Maybe you can find a used one somewhere if you look for one.

<<<-- Originally posted by Mathieu Ghekiere : Jiggy: Yes the 16x II lens is the one that comes with the XL1S.
If you want a complete manual lens, you have to buy them seperately (they are rather expensive, but hey, lenses always are). Maybe you can find a used one somewhere if you look for one. -->>>

thanks mathieu for that clarification. no, i don't think i need one do i? i have not seen any problems so far but i am doing rather simple work with the XLS1: studio shots, classroom trainings, events, etc.. most of the work I do is on a tripod with IS off. but i am planning on making a real short soon, and all this talk here on the forum of focus problems has me spooked. thanks!
jigs

Héhé, I don't know if you need one :-) I only have my XL1S for two weeks or so, so I really can't tell you very much information :-). I don't see real problems either, although I understand why other people would want it, and maybe one day, if I have more money and if I'm doing more complicated stuff and have more experience, I'll buy myself one.
Good luck.